1. Field of the Invention
This invention relates, in general, to electronic circuits and, in particular, to electronic circuits that control abrupt transients during amplifier power-up and power-down operations.
2. Related Art
In conventional amplifiers, electronic operations that either power-up or power-down an amplifier may cause abrupt transients that surge the output of the amplifier causing unpleasant audible noises (commonly referred to as a “pops”) when the output of the amplifier is utilized to drive a coupled load (such as, for example, an audio speaker or headset). Unfortunately, this situation is a problem because not only are these “pops” unpleasant to a listener but they may also damage the coupled load because the abrupt transients may surge the output of the amplifier to a power level capable of damaging either the audio speakers or headset.
In an automotive environment, as an example, this problem is difficult to solve due to multiple factors such as: a varying system voltage; a sound proofed quiet cabin; and listeners located in close proximity to multiple, highly sensitive speakers. Unfortunately, known techniques for attempting to solve this problem adversely affect other aspects of the system.
As an example, a conventional attempt to partially solve this problem has been to improve the transients by correspondingly attempting to improve the transition performance of the amplifier by gradually powering down the power state of the amplifier in a controlled manner. Typically, this is done by utilizing an RC circuit that provides an exponential voltage curve to the amplifier in order to control the power-down and power-up operations of the amplifier. Unfortunately, this exponential voltage curve is non-linear and, therefore, the resulting powering-down and powering-up times of the amplifier are different.
As a result, there is a need for a new circuit and method capable of controlling the resulting abrupt transients caused by either powering up or powering down an amplifier without utilizing a circuit that provides the amplifier with a voltage signal that is characterized by a non-linear voltage curve.